This invention relates to stuffer crimping of textile strands and is particularly concerned with a control method and apparatus for discharging the yarn from the crimping chamber. Control of discharge from a stuffer box during crimping of textile strands is known in the art in U.S. Pat. No. 3,859,695 and U.S. Pat. No. 3,528,149 . These patents and some of the patents cited as references thereto, teach sensing pressure or using photo cells to sense position or density of a compacted mass or wad of yarn as it unfolds from the crimping chamber and controlling the gate pressure at the exit of the crimping chamber. U.S. Pat. No. 3,777,338 teaches sensing yarn plug location in a stuffer tube of a steam jet texturing device by issuing a jet of fluid and sensing back pressure on the jet of fluid as it impinges on the yarn. The cited references to U.S. Pat. No. 3,777,338 also teach various means of sensing plug end control.
The prior art stuffer box crimping process for synthetic yarn comprises forcing the yarn into a crimping chamber to form a compressed mass or wad of the yarn in the crimping chamber, with the chamber having a pressure regulated discharge means at the outlet and discharging yarn from the crimping chamber. Controlling the discharge of the yarn from the chamber by regulating the pressure on the discharge means by varying the regulating pressure in response to sensing position of the wad of yarn at the exit of the crimping chamber and regulating the pressure with a pressure sensor controller is also known.
The prior art apparatus for stuffer box crimping of synthetic yarns comprises means to force the yarn into a crimping chamber having a regulated discharging means and a pressure sensor controller to regulate the position of the wad of the yarn in the crimping chamber by regulating pressure on the discharge means.